If you're in a hurry to take it apart instead of ordering a spring vise, there are several other ways to do it. None involve using vise grips or pliers.
1. First cock the lock.
2. Tighten a small crescent wrench on the spring, OR
3. Slide a small open-end wrench on the spring, OR
4. Make a spring cramp by filing the appropriate sized slot in a piece of metal, THEN
5. Loosen the tension on the spring and remove it.